rspec/rules/S1862/plsql/rule.adoc

A ``CASE`` and a chain of ``IF``/``ELSIF`` statements is evaluated from top to bottom. At most, only one branch will be executed: the first one with a condition that evaluates to ``true``. 

Therefore, duplicating a condition automatically leads to dead code. Usually, this is due to a copy/paste error. At best, it's simply dead code and at worst, it's a bug that is likely to induce further bugs as the code is maintained, and obviously it could lead to unexpected behavior. 

== Noncompliant Code Example

----
IF param == 1 THEN
  x := 'A';
ELSIF param == 2 THEN
  x := 'B';
ELSIF param == 1 THEN -- Noncompliant, for sure this is a bug
  x := 'C';
END IF;

result := CASE param
   WHEN 1 THEN 'A'
   WHEN 2 THEN 'B'
   WHEN 1 THEN 'C'  -- Noncompliant
   ELSE 'D'
END;
----

== Compliant Solution

----
IF param == 1 THEN
  result := 'A';
ELSIF param == 2 THEN
  result := 'B';
ELSIF param == 3 THEN
  result := 'C';
END IF;

result := CASE param
   WHEN 1 THEN 'A'
   WHEN 2 THEN 'B'
   WHEN 3 THEN 'C'
   ELSE 'D'
END;
----

include::../see.adoc[]